IX Black Hole Workshop

Guimarães 19-20 December 2016

Particle collisions are considered within the context of f(R) gravity described by f(R)=R+2\alpha \sqrt{R}, where R stands for the Ricci scalar and \alpha is a non-zero constant. The center of mass (CM) energy of head-on colliding particles moving in opposite radial directions near the horizon (for \alpha <0) grows unbounded. Collision of particles in the same direction yields finite energy which is of no interest. We note that an outgoing geodesic particle can be considered as the yield of a decay process of the black hole near the horizon. Addition of a cosmological constant does not change the feature. When the collision occurs near a non- black hole, i.e. a naked singularity (for \alpha >0), the particles gain unbounded CM energy. Collision of a massless outgoing Hawking photon with an infalling particle and collision of two oppositely moving photons following null-geodesics are also taken into account.